Calibration station for a printhead adapted to compensate for the wavelength sensitivity of an image recording material

Abstract

A calibration station ( 34 ) for a printhead ( 20 ) adapted to provide a beam of electromagnetic radiation from a variable electromagnetic energy source onto a sensitive radiation medium, the calibration station ( 34 ), incorporates a sensor ( 26 ) disposed for sensing the beam ( 16 ) provided by the printhead ( 20 ), wherein the sensor ( 26 ) provides an output sensor signal indicative of the sensed power of the beam ( 16 ). A control circuit is adapted to accept the output sensor signal from the sensor and adjusts the variable electromagnetic energy source. A filter is disposed in the path of the beam ( 16 ) between the printhead ( 20 ) and sensor ( 26 ), adapted to transmit to the sensor ( 26 ) a portion of incident electromagnetic radiation over a predefined range of wavelengths, dependent upon a measured response characteristic of the radiation-sensitive medium.

What is claimed is:  
     
       1. A feedback-control station for a printhead adapted to provide a beam of electromagnetic radiation from a variable electromagnetic energy source onto a radiation sensitive medium said feedback-control station comprising: 
       a sensor disposed for sensing said beam provided by said printhead, wherein said sensor provides an output sensor signal indicative of a sensed power of said beam;  
       a control circuit adapted to accept said output sensor signal from said sensor, wherein said control circuit adjusts said variable electromagnetic energy source;  
       a filter disposed in the path of said beam between said printhead and said sensor as well as between said printhead and said radiation sensitive medium, said filter adapted to convey to said sensor a first portion of incident electromagnetic radiation and to convey to said radiation sensitive medium a second portion of incident electromagnetic radiation over a predefined range of wavelengths dependent upon a response characteristic of said radiation sensitive medium; and  
       wherein response characteristics of said radiation sensitive medium are recorded on said medium.  
     
     
       2. The feedback-control station of  claim 1  wherein said beam of electromagnetic radiation is comprised of multiple beams. 
     
     
       3. The feedback-control station of  claim 1  wherein said beam of electromagnetic radiation is in a visible spectrum. 
     
     
       4. The feedback-control station of  claim 1  wherein said beam of electromagnetic radiation is in an infrared spectrum. 
     
     
       5. The feedback-control station of  claim 1  wherein said sensor is a photodiode. 
     
     
       6. The feedback-control station of  claim 1  wherein said medium comprises a colorant donor. 
     
     
       7. The feedback-control station of  claim 6  wherein said colorant donor comprises a dye. 
     
     
       8. The feedback-control station of  claim 6  wherein said colorant donor comprises a pigment. 
     
     
       9. The feedback-control station of  claim 6  wherein said colorant donor comprises an ink. 
     
     
       10. The feedback-control station of  claim 1  wherein said medium comprises a printing plate. 
     
     
       11. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is a laser. 
     
     
       12. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is a diode laser. 
     
     
       13. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is a LED. 
     
     
       14. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is an x-ray emitter. 
     
     
       15. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is incandescent lamp. 
     
     
       16. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is a halogen lamp. 
     
     
       17. The feedback-control station of  claim 1  wherein said variable electromagnetic energy source is an arc lamp. 
     
     
       18. The feedback-control station of  claim 1  wherein said filter is an absorptive filter. 
     
     
       19. The feedback-control station of  claim 1  wherein said filter is an interference filter. 
     
     
       20. The feedback-control station of  claim 1  further comprising a scattering medium which attenuates said beam, located between said printhead and said sensor. 
     
     
       21. The feedback-control station of  claim 1  wherein said control circuit adjusts said variable electromagnetic energy source by varying a drive current to said variable electromagnetic energy source. 
     
     
       22. The feedback-control station of  claim 1  wherein said control circuit adjusts said variable electromagnetic energy source by varying a time interval of a pulse width delivered to said variable electromagnetic energy source. 
     
     
       23. The feedback-control station of  claim 1  wherein said control circuit adjusts said variable electromagnetic energy source during exposure of said sensitive medium. 
     
     
       24. The feedback-control station of  claim 1  wherein said beam of electromagnetic radiation is an ultraviolet beam. 
     
     
       25. The feedback-control station of  claim 1  wherein said radiation sensitive medium is a silver halide material. 
     
     
       26. The feedback-control station of  claim 1  wherein said radiation sensitive medium is a photolithographic slide. 
     
     
       27. The feedback-control station of  claim 1  wherein said sensor senses the response characteristics of said radiation sensitive medium. 
     
     
       28. The feedback-control station as in  claim 1  wherein said filter is replaced to match the response characteristics of said radiation sensitive medium. 
     
     
       29. A feedback-control station for a printhead adapted to provide a beam of electromagnetic radiation from a variable electromagnetic energy source onto a radiation sensitive medium said feedback-control station comprising: 
       a sensor disposed for sensing said beam provided by said printhead, wherein said sensor provides an output sensor signal indicative of a sensed power of said beam;  
       a control circuit adapted to accept said output sensor signal from said sensor, wherein said control circuit adjusts said variable electromagnetic energy source;  
       a filter disposed in the path of said beam between said printhead and said sensor as well as between said printhead and said radiation sensitive medium, said filter adapted to convey to said sensor a first portion of incident electromagnetic radiation and to convey to said radiation sensitive medium a second portion of incident electromagnetic radiation over a predefined range of wavelengths dependent upon a response characteristic of said radiation sensitive medium; wherein:  
       said conveyance of said first portion of said beam of electromagnetic radiation to said sensor is accomplished by reflection from said filter acting as a beamsplitting filter;  
       said conveyance of said second portion of said beam of electromagnetic radiation to said radiation sensitive medium is accomplished by transmission through said beamsplitting filter;  
       said reflectance obeying relationship            R   filtersplitter          [   λ   ]       =       1   -       A   filtersplitter          [   λ   ]           1   +           S   sensor          [   λ   ]           A   colorant          [   λ   ]                           P     colorant   ,   goal         F     sensor   ,   goal                               
        while said transmission through said filter obeying relationship              T   filtersplitter          [   λ   ]       =       1   -       A   filtersplitter          [   λ   ]           1   +           A   colorant          [   λ   ]           S   sensor          [   λ   ]                           F     sensor   ,   goal         P     colorant   ,   goal                 ;                   
        wherein:  
       λ is the wavelength of the beam of electromagnetic radiation from the variable electromagnetic energy source directed upon the radiation-sensitive medium;  
       T filtersplitter [λ] is the fraction of power of the beam of electromagnetic radiation from the variable electromagnetic energy source transmitted by the feedback-controlling filter at wavelength λ;  
       R filtersplitter [λ] is the fraction of power of the beam reflected by the feedback-controlling filter at wavelength λ;  
       A filtersplitter [λ] is the fraction of power of the beam absorbed by the feedback-controlling filter at wavelength λ;  
       S sensor [λ] is the signal produced by the calibration sensor in response to the power of the beam at wavelength λ;  
       F sensor,goal  is the signal produced by the calibration sensor in response to the power of the beam directed upon said sensor by the feedback-controlling filter when the power of said beam directed simultaneously upon the radiation-sensitive medium by the feedback-controlling filter at the same wavelength produces the goal level of response; and  
       P colorant,goal  is the power of the beam absorbed in the radiation-sensitive medium producing the goal level of response.  
     
     
       30. The feedback-control station of  claim 29  wherein: 
       said filter is a beamsplitting filter.